Geography Reference
In-Depth Information
A similar effort is taking place for neobiogeographic classification (see
ht-
Biogeographic regionalization implies the recognition of successively nested
areas. These areas should be natural; that is, they should correspond to bi-
otic components. Classically, the following five categories have been used:
realm, region, dominion, province,
and
district.
Whenever more categories
are necessary, the prefix
sub-
may be added to them (e.g.,
subregion, sub-
province
).
Sometimes it is more difficult to determine the exact boundaries of two
realms or regions. For example, Müller (1979) found eighteen proposed
ult, authors have described transition zones (Darlington 1957; Halffter 1987;
Ruggiero and Ezcurra 2003), which represent events of biotic hybridization,
promoted by historical and ecological changes that allowed the mixture of
different biotic components. Transition zones may have depauperate biotas,
but in some cases they harbor a particularly high biodiversity. From the evol-
utionary viewpoint, transition zones deserve special attention because they
represent areas of intense biotic interaction. The analysis of transition zones
by ecological biogeographers is mostly quantitative, whereas for evolution-
ary biogeographers it is qualitative. In panbiogeographic analyses, trans-
ition zones are indicated by the presence of nodes (Escalante et al. 2004),
whereas in cladistic biogeographic analyses, putative transition zones give
conflicting results because they appear to be sister areas to different areas.
